Best bang for the buck CPU's... AMD Phenom II X4 955 or Intel Core i5 750
With that said, a budget is an important fact. For example running a Athlon II X3 440 & 5870 is a better gaming System versus an i5 750 & 5770.
Intel Core I7-980X is the most powerful desktop processor on the market right now and it retails for around $1,000.00. However with that said, it's only a few percentage points better than an I7 930 which can easily be found for $300.00.